Deformation and flow of stiff pastes: review of rheology of some soft solids

This paper reviews modelling and supporting experimental work that provides insight into the nature of stiff ceramic pastes. These pastes consist of discrete powder particles in a matrix of viscous fluid. At sufficiently high particle volume fractions such pastes are able to withstand, without excessive deformation, the forces usual during handling of green ceramics. First, the industrial motivation for the study of pastes is examined, paying special attention to difficulties which are often glossed over in the open literature but which the present authors know from first hand experience. Common test methods are then discussed, and theories are outlined that hare been developed to explain or generalise the experimental results. The penultimate section reviews some of the progress that has been made in applying theory to industrially based problems. The approach pioneered in the discipline of soil mechanics appears particularly promising as a basis for developing models of pastes that give some physical insight into their mechanical behaviour, and so might give a link to mix design. In conclusion a look into the future of the study of pastes is presented.